Java Collections用法及代碼示例

// Java Program to Demonstrate Adding Elements 
// Using addAll() method 
  
// Importing required classes 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.List; 
  
// Main class 
class GFG { 
  
    // Main driver method 
    public static void main(String[] args) 
    { 
        // Creating a list 
        // Declaring object of string type 
        List<String> items = new ArrayList<>(); 
  
        // Adding elements (items) to the list 
        items.add("Shoes"); 
        items.add("Toys"); 
  
        // Add one or more elements 
        Collections.addAll(items, "Fruits", "Bat", "Ball"); 
  
        // Printing the list contents 
        for (int i = 0; i < items.size(); i++) { 
            System.out.print(items.get(i) + " "); 
        } 
    } 
}

// Java program to demonstrate sorting 
// a Collections using sort() method 
  
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.List; 
  
// Main Class 
// SortingCollectionExample 
class GFG { 
  
    // Main driver method 
    public static void main(String[] args) 
    { 
        // Creating a list 
        // Declaring object of string type 
        List<String> items = new ArrayList<>(); 
  
        // Adding elements to the list 
        // using add() method 
        items.add("Shoes"); 
        items.add("Toys"); 
  
        // Adding one or more elements using addAll() 
        Collections.addAll(items, "Fruits", "Bat", "Mouse"); 
  
        // Sorting according to default ordering 
        // using sort() method 
        Collections.sort(items); 
  
        // Printing the elements 
        for (int i = 0; i < items.size(); i++) { 
            System.out.print(items.get(i) + " "); 
        } 
  
        System.out.println(); 
  
        // Sorting according to reverse ordering 
        Collections.sort(items, Collections.reverseOrder()); 
  
        // Printing the reverse order 
        for (int i = 0; i < items.size(); i++) { 
            System.out.print(items.get(i) + " "); 
        } 
    } 
} 

// Java Program to Demonstrate Binary Search 
// Using Collections.binarySearch() 
  
// Importing required classes 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.List; 
  
// Main class 
// BinarySearchOnACollection 
public class GFG { 
  
    // Main driver method 
    public static void main(String[] args) 
    { 
        // Creating a List 
        // Declaring object of string type 
        List<String> items = new ArrayList<>(); 
  
        // Adding elements to object 
        // using add() method 
        items.add("Shoes"); 
        items.add("Toys"); 
        items.add("Horse"); 
        items.add("Ball"); 
        items.add("Grapes"); 
  
        // Sort the List 
        Collections.sort(items); 
  
        // BinarySearch on the List 
        System.out.println( 
            "The index of Horse is "
            + Collections.binarySearch(items, "Horse")); 
  
        // BinarySearch on the List 
        System.out.println( 
            "The index of Dog is "
            + Collections.binarySearch(items, "Dog")); 
    } 
}

// Java Program to Demonstrate Copying Elements 
// Using copy() method 
  
// Importing required classes 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.List; 
  
// Main class 
// CopyOneCollectionToAnother 
class GFG { 
  
    // Main driver method 
    public static void main(String[] args) 
    { 
        // Create destination list 
        List<String> destination_List = new ArrayList<>(); 
  
        // Add elements 
        destination_List.add("Shoes"); 
        destination_List.add("Toys"); 
        destination_List.add("Horse"); 
        destination_List.add("Tiger"); 
  
        // Print the elements 
        System.out.println( 
            "The Original Destination list is "); 
  
        for (int i = 0; i < destination_List.size(); i++) { 
            System.out.print(destination_List.get(i) + " "); 
        } 
        System.out.println(); 
  
        // Create source list 
        List<String> source_List = new ArrayList<>(); 
  
        // Add elements 
        source_List.add("Bat"); 
        source_List.add("Frog"); 
        source_List.add("Lion"); 
  
        // Copy the elements from source to destination 
        Collections.copy(destination_List, source_List); 
  
        // Printing the modified list 
        System.out.println( 
            "The Destination List After copying is "); 
  
        for (int i = 0; i < destination_List.size(); i++) { 
            System.out.print(destination_List.get(i) + " "); 
        } 
    } 
}

// Java Program to Illustrate Working of Disjoint Function 
  
// Importing required classes 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.List; 
  
// Main class 
// DisjointCollectionsExample 
class GFG { 
  
    // Main driver method 
    public static void main(String[] args) 
    { 
        // Create list1 
        List<String> list1 = new ArrayList<>(); 
  
        // Add elements to list1 
        list1.add("Shoes"); 
        list1.add("Toys"); 
        list1.add("Horse"); 
        list1.add("Tiger"); 
  
        // Create list2 
        List<String> list2 = new ArrayList<>(); 
  
        // Add elements to list2 
        list2.add("Bat"); 
        list2.add("Frog"); 
        list2.add("Lion"); 
  
        // Check if disjoint or not 
        System.out.println( 
            Collections.disjoint(list1, list2)); 
    } 
}